What are the biggest red flags when hiring an HVAC contractor?

HVAC red flags cluster around three patterns: false diagnosis (filter problem framed as compressor failure), refrigerant scams (top-up without leak search), and oversized/undersized equipment (no real Manual J load calculation). The downsides are unnecessary $8,000-$15,000 replacements, ongoing refrigerant costs from undisclosed leaks, and systems that short-cycle or run continuously.

"Your compressor is dying." The single most-cited HVAC misdiagnosis. The technician arrives for a no-cool call, runs a quick pressure check, and announces the compressor is failing. In reality, 60%+ of no-cool calls are clogged filters, dirty condenser coils, refrigerant leaks (low charge), bad capacitors ($15 part), or contactor failures ($30 part). Demand a multi-step diagnosis with measurements: superheat/subcool, return/supply temperature split, condenser fan amp draw, compressor amp draw vs. rated load. A real diagnosis takes 30-60 minutes and produces numbers you can verify.

Refrigerant top-up without a leak search. A sealed refrigerant loop should never lose refrigerant. If the system is low, there is a leak. A technician who "tops off" the refrigerant and leaves is selling you refrigerant you'll keep losing — and EPA rules require leak detection and repair on systems over 50 lbs (commercial) and best practice on residential. Either insist on a leak search (electronic detector or UV dye) or replace the line set if the leak can't be found. Refrigerant prices have climbed steeply as R-22 was phased out; a "top up" can be $200-$800 and recurs.

No EPA 608 certification. Federal law requires EPA 608 to handle refrigerant. Type II for high-pressure (most residential), Universal for all types. A technician without 608 cannot legally recover or charge refrigerant. EPA 608 is verifiable at the certifying body.

No Manual J load calculation for new system sizing. Replacing a 4-ton system with a 4-ton system is not engineering — it's lazy quoting. A proper sizing requires Manual J (heat load by room), Manual S (equipment selection from Manual J), and Manual D (duct design). HVAC contractors who skip Manual J typically oversize, leading to short-cycling, poor dehumidification, and reduced equipment life. Ask to see the Manual J output. "Rule of thumb" sizing is a red flag.

Missing state license or wrong class. California C-20, Texas TDLR Class A or B, Florida CAC/CMC, Arizona ROC C-39. Verify the license is active and the class covers the tonnage being installed.

Large upfront deposit. Above 10-15%, demanded in cash, is a phoenix risk. California caps at 10% or $1,000.

"You need new ductwork too." Sometimes true, often upsell. A real ductwork recommendation comes from measured leakage (Duct Blaster test, typically expressed as CFM25 per 100 sq ft of floor area) and visible damage in attic/crawl photos. "I just looked at it and it's bad" is not evidence.

Manufacturer-brand pressure ("you must buy Carrier/Trane/Lennox"). The brand matters less than the installation quality. A poorly-installed Carrier system performs worse than a well-installed Goodman. Push back if the pitch is brand-centric instead of installation-centric.

Groundcheck (earthmove.io/trust) verifies the state HVAC license, EPA 608 where available, prior complaints, and phoenix-company patterns. It does not verify Manual J calculations or refrigerant leak honesty — get a second quote on anything over $5,000.